The Collaborative International Dictionary of English v.0.48:

Calking \Calk"ing\, n.
   The act or process of making seems tight, as in ships, or of
   furnishing with calks, as a shoe, or copying, as a drawing.
   [1913 Webster]

   Calking iron, a tool like a chisel, used in calking ships,
      tightening seams in ironwork, etc.
      [1913 Webster]

            Their left hand does the calking iron guide.
                                                  --Dryden.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Calk \Calk\ (k[add]k), v. t. [imp. & p. p. Calked; p. pr. &
   vb. n. Calking.] [Either corrupted fr. F. calfater (cf. Pg.
   calafetar, Sp. calafetear), fr. Ar. qalafa to fill up
   crevices with the fibers of palm tree or moss; or fr. OE.
   cauken to tred, through the French fr. L. calcare, fr. calx
   heel. Cf. Calk to copy, Inculcate.]
   1. To drive tarred oakum into the seams between the planks of
      (a ship, boat, etc.), to prevent leaking. The calking is
      completed by smearing the seams with melted pitch.
      [1913 Webster]

   2. To make an indentation in the edge of a metal plate, as
      along a seam in a steam boiler or an iron ship, to force
      the edge of the upper plate hard against the lower and so
      fill the crevice.
      [1913 Webster]